I’ve been meaning to post this somewhere useful for a while now, so here it is.
Assumption
Machine A wants to connect with SSH without passwords (with cert) to Machine B
Method
On Machine A:
[bash]
ssh-keygen
[/bash]
Make sure you pick no pass phrase.
[bash]
scp .ssh/id_rsa.pub user@machineb:.ssh/id_rsa.tmp
[/bash]
On Machine B:
[bash]
cat id_rsa.tmp >> authorized_keys
chmod 600 authorized_keys
[/bash]
Connect as normal from machine A to machine B